I hate zebra danios. The little buggers in my tank are constantly zipping around and chasing eachother. They're also freakin' pigs. They'll frequently consume any and all floating flakes before they even touch the gravel. They also tend to intimidate my honey gouramis with their behavior. The gouramis are kind of timid and just look at the zebras and seem to think, "What the hell is wrong with those guys?"
I don't know. Maybe they're just a little too active for my tastes. I will say that they are very hardy and don't seem to harass any of my other fish or ghost shrimp. They're just really, really active. I'm mostly annoyed by them because I would like to see my gouramis swim more towards the upper middle levels, like they're supposed to. But, because the zebras occupy this level, and because they're on crack, the gouramis don't tend to go up that high. Very disappointing. I'm thinking of seeing if my LFS will take them back for a credit or something. They're so cheap, though. I don't know what I could possibly get for them. Also, nothing in the research that I did said that they would be so hyperactive.
Bottom line; if you're not looking for speed freak fish, stay away from zebras.